This invention relates to a current supply circuit arrangement having an output to which a supply voltage is supplied through a diode and which comprises a capacitor, to which the charging voltage of an an auxilliary voltage source is supplied through a further diode, which charging voltage exceeds the supply voltage.
DE OS 33 00 222 discloses a system for resetting a switching circuit comprising a microprocessor in the case of mains failure or when the mains voltage temporarily falls below a given limit value, in which circuit, after the occurrence of these conditions, a capacitor coupled to a supply voltage is discharged by means of a transistor controlled by a voltage control circuit. The input of a voltage stabilization circuit is connected to the first capacitor and the output voltage of this circuit is supplied to a microcomputer, which comprises the microprocessor. Upon failure of the mains voltage, the first capacitor applied to the supply voltage is applied through the transistor to a higher supply voltage of a second capacitor. In the normal case, the voltage at the second capacitor has double the value of the supply voltage for the microcomputer.
Due to the supply of a capacitor with a higher voltage than the supply voltage, a larger quantity of energy can be stored in the capacitor, which permits a longer bridging of mains failures. For this purpose, the additionally required higher supply voltage must be derived from the additional supply voltage source, which can apply a corresponding current for charging the capacitor in order to guarantee the readiness for operation of such an emergency current supply already after a sufficient period of time. This high current load capacity of the additional voltage source requires larger dimensions of the apparatus and leads to a corresponding higher cost.